Planar sputtering magnetrons are well known in the art, as exemplified by see U.S. Pat. No. 4,200,510 and the references cited therein, and the text, B. Chapman, Glow Discharge Processes, pp. 260-270, J. Wiley & Sons (1980).
Planar sputtering magnetrons generally comprise an anode assembly and a rectangular cathode assembly spaced from the anode assembly and having one or more consumable metal target members. The anode and cathode assemblies are disposed in a vacuum chamber into which a non-oxidizing gas, such as argon, is introduced. A magnetic field is generated across the cathode assembly which is subjected to a negative voltage sufficient to ionize the gas atoms and impel them against the target member(s), causing surface portions of the target member(s) to be sputtered and in turn to be deposited as a film on a substrate positioned proximate to the cathode assembly. The magnetic field is used to enhance ionizaton of the gas at lower voltages.
In manufacturing planar magnetron sputtering equipment it has been recognized that the useful life of the consumable cathode assembly is limited because of a "race track" erosion phenomenon. The term "race track" is used because the applied magnetic field tends to restrict the sputtering erosion of the target to an area in the form of a flat oval.